/// <exception cref="IOException"/>
protected static short EvaluateMaxFragmentLengthExtension(bool resumedSession, IDictionary clientExtensions,
IDictionary serverExtensions, byte alertDescription)
{
short maxFragmentLength = TlsExtensionsUtilities.GetMaxFragmentLengthExtension(serverExtensions);
if (maxFragmentLength >= 0)
{
if (!MaxFragmentLength.IsValid((byte)maxFragmentLength) ||
(!resumedSession && maxFragmentLength != TlsExtensionsUtilities
.GetMaxFragmentLengthExtension(clientExtensions)))
{
throw new TlsFatalAlert(alertDescription);
}
}
return(maxFragmentLength);
}
public virtual void ProcessClientExtensions(IDictionary clientExtensions)
{
this.mClientExtensions = clientExtensions;
if (clientExtensions != null)
{
this.mEncryptThenMacOffered = TlsExtensionsUtilities.HasEncryptThenMacExtension(clientExtensions);
this.mMaxFragmentLengthOffered = TlsExtensionsUtilities.GetMaxFragmentLengthExtension(clientExtensions);
if (mMaxFragmentLengthOffered >= 0 && !MaxFragmentLength.IsValid((byte)mMaxFragmentLengthOffered))
{
throw new TlsFatalAlert(AlertDescription.illegal_parameter);
}
this.mTruncatedHMacOffered = TlsExtensionsUtilities.HasTruncatedHMacExtension(clientExtensions);
this.mSupportedSignatureAlgorithms = TlsUtilities.GetSignatureAlgorithmsExtension(clientExtensions);
if (this.mSupportedSignatureAlgorithms != null)
{
/*
* RFC 5246 7.4.1.4.1. Note: this extension is not meaningful for TLS versions prior
* to 1.2. Clients MUST NOT offer it if they are offering prior versions.
*/
if (!TlsUtilities.IsSignatureAlgorithmsExtensionAllowed(mClientVersion))
{
throw new TlsFatalAlert(AlertDescription.illegal_parameter);
}
}
this.mNamedCurves = TlsEccUtilities.GetSupportedEllipticCurvesExtension(clientExtensions);
this.mClientECPointFormats = TlsEccUtilities.GetSupportedPointFormatsExtension(clientExtensions);
}
/*
* RFC 4429 4. The client MUST NOT include these extensions in the ClientHello message if it
* does not propose any ECC cipher suites.
*
* NOTE: This was overly strict as there may be ECC cipher suites that we don't recognize.
* Also, draft-ietf-tls-negotiated-ff-dhe will be overloading the 'elliptic_curves'
* extension to explicitly allow FFDHE (i.e. non-ECC) groups.
*/
//if (!this.mEccCipherSuitesOffered && (this.mNamedCurves != null || this.mClientECPointFormats != null))
// throw new TlsFatalAlert(AlertDescription.illegal_parameter);
}